Stents and other prosthetic devices have provided the means to clinically treat many conditions. Stents are commonly used to open blood vessels, e.g. clearing obstructions, preventing restenosis, providing support at the site of an aneurysm, and to repair damage to vascular tissues, e.g. arteries and veins. In addition to blood vessels, other vessels of the body may be repaired with a stent, including the trachea for breathing disorders, renal and urethral tubules, fallopian tubes for the treatment of infertility, eustachian tubes for the treatment of chronic ear infection and other hearing disorders, large and small intestines where the vessels may be occluded with tumor cells, etc.
Many stent designs are known and in clinical use. For example, they can be cut from a tube or formed from a wire that has been bent back and forth in a zig-zag pattern and wound in a circumferential direction to form one or more loops of a pre-determined circumference. Typically, the stent is radially expandable from a collapsed condition. Once in position, it is expanded to the predetermined size, to support and reinforce the lumen.
One of the largest fields for the use of stents is in the treatment of cardiovascular disease. Treatment by balloon angioplasty, percutaneous transluminal angioplasty (PTA), has been shown to improve life expectancy after occlusion of blood vessels, but up to 40% of patients encounter restenosis within 6 months. Since angioplasty alone is marked by progressive luminal compromise (negative remodeling), stenting has become the leading interventional strategy with current application in 60–70% of PTAs. Stent use offers a number of advantages over simple PTA, including decreased early in-hospital complications, increase in luminal diameter, decreased negative remodeling, and sealing of intimal flaps. However, arteries treated with stents also encounter dramatically accelerated rates of in-stent restenosis, which are clinically significant in up to 40% of cases. Smooth muscle proliferation and vascular remodeling; restenosis after stent deployment is due almost entirely to smooth muscle hyperplasia and matrix proliferation. In-stent neointima formation thus remains a major procedural limitation for stent use, limiting both utilization and long-term clinical benefits.
There has been interest in the development of a drug delivery platform that can provide local delivery of pharmaceuticals, for example, the delivery of anti-restenotic drugs; anti-proliferative agents for the treatment of tumors; antibiotics in the treatment of chronic ear infection, and the like. While systemic administration of drugs or other biologically-active substances is satisfactory for some medical treatments, many other treatments can be facilitated and/or improved with local drug delivery or administration to selected portions of internal body tissues. Localized drug administration is particularly advantageous where drug retention in the treated locus is required for an effective period of time without appreciably affecting other body tissues
The development of stents for drug delivery is of great interest for the treatment of a variety of conditions. The present invention addresses this problem.
Relevant Art
U.S. Pat. No. 6,004,346, “Intralumenal drug eluting prosthesis” discloses a drug eluting stent. U.S. Pat. No. 5,972,027 discloses a porous stent drug delivery system. A drug eluting stent is described in U.S. Pat. No. 5,697,967. U.S. Pat. No. 6,335,029 is directed to polymeric coatings for controlled delivery of active agents. Other coatings for localized delivery of drug agents are disclosed in U.S. Pat. No. 6,280,411. Brown et al., U.S. Pat. No. 6,071,305 relates to a directional drug delivery stent. A drug delivery stent for liquid formulations is disclosed by Leone et al., U.S. Pat. No. 5,891,108.
Reviews of the field of local drug delivery, and the treatment of restenosis may be found in Ettenson and Edelman (200) Vasc Med 5(2):97–102; Gunn and Cumberland (1999) Eur Heart J 20(23):1693–700; and Raman and Edelman (1998) Semin Interv Cardiol 3(3–4):133–7; among others.